Compiler crash when using CanThrow

[alexandru]

Compiler version

3.4.1

Minimized code

#!/usr/bin/env -S scala-cli shebang

//> using scala "3.4.1"
//> using option -experimental

trait MyEvidence

type ContextFn[+T] = (MyEvidence, CanThrow[Exception]) ?=> T

class Foo:
    def foo: ContextFn[String] =
        "foo"

class Bar:
    val foo = new Foo

    def bar: ContextFn[String] =
        foo.foo +
        "bar"

Output

Compiling project (Scala 3.4.1, JVM (21))
Error compiling project (Scala 3.4.1, JVM (21))
Error: Unexpected error when compiling directio_5eb7d97420-5bb168c9c8: java.lang.AssertionError: assertion failed: bad adapt for this.foo().foo: (using x$1: MyEvidence): String
	at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
	at dotty.tools.dotc.transform.Erasure$Boxing$.adaptToType(Erasure.scala:391)
	at dotty.tools.dotc.transform.Erasure$Typer.adapt(Erasure.scala:1091)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
	at dotty.tools.dotc.transform.Erasure$Typer.typedSelect(Erasure.scala:671)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3088)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
	at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3389)
	at dotty.tools.dotc.transform.Erasure$Typer.typedApply(Erasure.scala:843)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3113)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
	at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
	at dotty.tools.dotc.transform.Erasure$Typer.typedSelect(Erasure.scala:671)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3088)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
	at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3389)
	at dotty.tools.dotc.transform.Erasure$Typer.typedApply(Erasure.scala:843)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3113)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
	at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3389)
	at dotty.tools.dotc.typer.Typer.$anonfun$62(Typer.scala:2603)
	at dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
	at dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:2603)
	at dotty.tools.dotc.transform.Erasure$Typer.typedDefDef(Erasure.scala:960)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3095)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
	at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3300)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3346)
	at dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1073)
	at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2790)
	at dotty.tools.dotc.transform.Erasure$Typer.typedClassDef(Erasure.scala:1049)
	at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3101)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3105)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
	at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3300)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3346)
	at dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1073)
	at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2923)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3147)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
	at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3389)
	at dotty.tools.dotc.transform.Erasure.run(Erasure.scala:144)
	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:354)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:333)
	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:360)
        ....

[Gedochao]

Full crash output:

 exception while retyping this.foo.foo.apply of class Select # -1

  An unhandled exception was thrown in the compiler.
  Please file a crash report here:
  https://github.com/scala/scala3/issues/new/choose
  For non-enriched exceptions, compile with -Yno-enrich-error-messages.

     while compiling: /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro/.scala-build/compiler-repro_ed26d7ea58-c6d3736935/src_generated/main/repro-script.scala
        during phase: MegaPhase{elimErasedValueType, pureStats, vcElideAllocations, etaReduce, arrayApply, elimPolyFunction, tailrec, completeJavaEnums, mixin, lazyVals, memoize, nonLocalReturns, capturedVars}
                mode: Mode(ImplicitsEnabled)
     library version: version 2.13.12
    compiler version: version 3.4.1
            settings: -classpath /Users/pchabelski/Library/Caches/Coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala3-library_3/3.4.1/scala3-library_3-3.4.1.jar:/Users/pchabelski/Library/Caches/Coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.12/scala-library-2.13.12.jar -d /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro/.scala-build/compiler-repro_ed26d7ea58-c6d3736935/classes/main -experimental true -java-output-version 17 -sourceroot /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro

Exception in thread "main" java.lang.AssertionError: assertion failed: bad adapt for this.foo().foo: (using x$1: repro$minusscript$_.this.MyEvidence): String
        at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
        at dotty.tools.dotc.transform.Erasure$Boxing$.adaptToType(Erasure.scala:391)
        at dotty.tools.dotc.transform.Erasure$Typer.adapt(Erasure.scala:1091)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.transform.Erasure$Typer.typedSelect(Erasure.scala:671)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3088)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3389)
        at dotty.tools.dotc.transform.Erasure$Typer.typedApply(Erasure.scala:843)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3113)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.transform.Erasure$Typer.typedSelect(Erasure.scala:671)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3088)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3389)
        at dotty.tools.dotc.transform.Erasure$Typer.typedApply(Erasure.scala:843)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3113)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3389)
        at dotty.tools.dotc.typer.Typer.$anonfun$62(Typer.scala:2603)
        at dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
        at dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:2603)
        at dotty.tools.dotc.transform.Erasure$Typer.typedDefDef(Erasure.scala:960)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3095)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3300)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3346)
        at dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1073)
        at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2790)
        at dotty.tools.dotc.transform.Erasure$Typer.typedClassDef(Erasure.scala:1049)
        at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3101)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3105)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3300)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3346)
        at dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1073)
        at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2790)
        at dotty.tools.dotc.transform.Erasure$Typer.typedClassDef(Erasure.scala:1049)
        at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3101)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3105)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3300)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3346)
        at dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1073)
        at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2923)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3147)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3389)
        at dotty.tools.dotc.transform.Erasure.run(Erasure.scala:144)
        at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:354)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.immutable.List.foreach(List.scala:333)
        at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:360)
        at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:315)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
        at dotty.tools.dotc.Run.runPhases$1(Run.scala:337)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:350)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:360)
        at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:69)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:360)
        at dotty.tools.dotc.Run.compileSources(Run.scala:261)
        at dotty.tools.dotc.Run.compile(Run.scala:246)
        at dotty.tools.dotc.Driver.doCompile(Driver.scala:37)
        at dotty.tools.dotc.Driver.process(Driver.scala:196)
        at dotty.tools.dotc.Driver.process(Driver.scala:164)
        at dotty.tools.dotc.Driver.process(Driver.scala:176)
        at dotty.tools.dotc.Driver.main(Driver.scala:206)
        at dotty.tools.dotc.Main.main(Main.scala)
Compilation failed

[hamzaremmal]

Minimization:

//> using options -experimental -Yno-experimental

import language.experimental.erasedDefinitions

erased trait A
trait B

def foo: (A, B) ?=> Nothing = ???
def bar: (A, B) ?=> Nothing = foo

It has nothing to do specifically with CanThrow. If you remove erased for A, or if the return type of foo is either A ?=> Nothing or B ?=> Nothing, it works.

[hamzaremmal]

Changing the signature of foo to A ?=> B ?=> Nothing crashes too for the same reason.

For now, I was able to narrow it down to the computation of integrateSelect in ContextFunctionResults

[odersky]

@hamzaremmal I wanted to take a look at it, but see you already have fixed it. That was fast!